Guide to developments in Missouri police shooting of Michael Brown

A protester tries to throw tear gas back at the police in Ferguson, Mo., Sunday, Aug. 17, 2014. Protests over the killing of 18-year-old Michael Brown by a white police officer have entered their second week. (AP Photo/St. Louis Post-Dispatch, J.B. Forbes)

FERGUSON, Mo. | After an unarmed black teenager was shot on Aug. 9 by a police officer in Ferguson, the city north of downtown St. Louis erupted into protests. Here's a look at key elements of the shooting and the unrest that followed:

THE LATEST: Missouri Gov. Jay Nixon ordered the National Guard to Ferguson early Monday, just hours after police used tear gas when another peaceful protest quickly deteriorated. Marchers had pushed toward one end of a street, and authorities — who said they were responding to reports of gunfire, looting, vandalism and protesters who hurled Molotov cocktails — pushed them back with tear gas. The streets were empty before a state-imposed midnight curfew.

Attorney General Eric Holder over the weekend ordered a federal medical examiner to perform a third autopsy on Brown. A preliminary private autopsy found he was shot at least six times, including twice in the head. Results of a state-performed autopsy have not been released.

THE SHOOTING: Police have said the officer was pushed into his squad car, then physically assaulted in the vehicle during a struggle over his weapon. At least one shot was fired inside the car. The struggle then spilled onto the street, where Brown was shot multiple times.

Dorian Johnson, who says he was with Brown at the time, has described a different story. He told reporters that the officer ordered him and Brown out of the street, then tried to open his door so close to the young men that it "ricocheted" back, apparently upsetting the officer. Johnson said the officer grabbed Brown's neck and tried to pull him into the car before brandishing his weapon. He said Brown started to run and the officer pursued him, firing multiple times. Johnson and another witness said Brown had his hands raised when the officer fired.

THE UNREST: Protesters have gathered nightly since Brown's death, with some looting stores, damaging buildings and vandalizing property. Police have used tear gas and smoke bombs, and some people hurled Molotov cocktails and rocks at officers. Officers from multiple departments in riot gear and military equipment have clashed with protesters, who often chant, "Hands up, don't shoot."

The governor has called in the National Guard to help. He also handed oversight of the protests to Highway Patrol Capt. Ron Johnson, who is from the Ferguson area.

THE POLICE TACTICS: The initial police response drew heavy criticism from around the nation. Critics said it was part of a law-enforcement trend toward more aggressive weapons and tactics. The American Civil Liberties Union in June released a report stating that police were overwhelmingly relying on SWAT raids — involving the use of assault rifles, battering rams and flash-bang grenades — for routine work such as searching for small amounts of drugs and serving warrants.

THE INVESTIGATION: At the request of Ferguson police, Brown's death is being investigated by St. Louis County police. The FBI also has opened an investigation into possible civil rights violations. According to the Highway Patrol, 40 FBI agents starting going door-to-door in the neighborhood on Saturday, talking to people who might have seen or have information about the shooting.